Previous scannerless laser ranging systems which operate with an amplitude-modulated continuous-wave (CW) laser source have generally utilized an image intensifier tube in the receiver (see e.g. U.S. Pat. Nos. 4,935,616 and 6,088,086 which are incorporated herein by reference). The image intensifier tube limits operation of these systems to the visible region and wavelengths below about one micron so that the prior scannerless laser ranging systems are generally not eye-safe for people in the field of view. Additionally, the image intensifier tube in these systems has a poor resolution of target features; and the image produced by the image intensifier tube is subject to blooming in the presence of a relatively high intensity of incident light (e.g. due to a glint from the target or elsewhere) which can further degrade the resolution. The temporal responsivity of the image intensifier tube is also limited by a relatively slow phosphor decay time.
The present invention overcomes the limitations of the prior art by providing a scannerless 3-D imaging apparatus which utilizes a variable attenuator in the form of a loss modulator in place of the conventionally-used image intensifier tube. The use of the loss modulator allows optical imaging directly onto an array detector, thereby providing a sharper image of the target and eliminating blooming which occurs in prior art devices based on image intensifier tubes. The loss modulator also extends the wavelength range over which the scannerless 3-D imaging apparatus of the present invention can be used so that operation at eye-safe wavelengths (e.g. 1.4-1.7 μm) is possible. This allows the possibility for new applications where concerns about exposure to laser radiation are paramount, including vehicle collision avoidance, autonomous rendezvous and docking, robotic vision, industrial inspection and measurement, 3-D cameras, and facial recognition.
These and other advantages of the present invention will become evident to those skilled in the art.